1. Field of the Invention
The present invention relates to a probe needle for a probe card, and a method of fabrication and control thereof. More particularly, the present invention relates to a cantilever type probe needle for a probe card, and a method of fabrication and control thereof.
2. Description of the Background Art
In the conventional process of fabricating a semiconductor device, an apparatus called a probe card is used in checking the electrical characteristics of a semiconductor device. FIG. 20 is a sectional view for describing a conventional probe card. Referring to FIG. 20, a conventional probe card has an opening 114 formed substantially at the center of a substrate 113. A plurality of probe needles 115 are arranged at the periphery of opening 114 towards the center of opening 114. Probe needles 115 are connected to terminals (not shown) arranged at the periphery of substrate 113 via a wire. These terminals are connected to a tester device called a prober during the inspection of a semiconductor device. The probe card is placed facing the surface of the semiconductor device which is the subject of inspection so as to have the leading end of probe needle 115 arranged to come into contact with an electrode formed at the surface of the semiconductor device. The electrical characteristics of this semiconductor device is inspected through probe needle 115 in contact with the electrode formed at the surface of semiconductor device.
FIG. 21 is a schematic diagram for describing the conventional probe needle of FIG. 20. Referring to FIG. 21, the lead portion of the probe needle has a diameter D of approximately 0.25 mm. The length L of the leading end 101 of the probe needle is approximately 7 mm. The tip portion 102 of the probe needle that forms contact with the electrode of the semiconductor device under test has a diameter d of approximately 50 .mu.m. Tungsten and the like is employed as the material of this probe needle.
The configuration of the leading end of a conventional probe needle will be described hereinafter with reference to the side views and perspective views of FIGS. 22-27.
FIGS. 22 and 23 show the configuration of the leading end of a conventional blast type probe needle. The tip 102 of the probe needle has substantially a plane configuration.
FIGS. 24 and 25 show the configuration of the leading end of a conventional specular type probe needle. The tip 102 of this probe needle has substantially a round configuration.
FIGS. 26 and 27 show the configuration of the leading end of a conventional spherical type probe needle. The substantially round configuration of tip 102 of this probe needle is formed to have a radius of curvature smaller than that of the specular type probe needle shown in FIGS. 24 and 25.
The contact process of a conventional probe needle with the electrode of a semiconductor device which is the subject of inspection in the process of checking the electrical characteristics of a semiconductor device will be described hereinafter with reference to the schematic diagrams of FIGS. 28 and 29.
Referring to FIG. 28, an electrode 105 formed at the surface of a semiconductor device 117 is brought into contact with tip 102 of the probe needle by elevating semiconductor device 117. Electrode 105 includes an aluminum layer 119 which is a conductor. An aluminum oxide layer 118 of approximately 30 .ANG. in thickness is formed at the surface of aluminum layer 119. As an alternative to aluminum layer 119, an alloy layer of aluminum and copper may be employed. Since aluminum oxide layer 118 is an insulator, electrical connection cannot be established between tip 102 of the probe needle and aluminum layer 119 by just bringing tip 102 of the probe needle into contact with the surface of electrode 105 as shown in FIG. 28.
Accordingly, semiconductor device 117 is further elevated as shown in FIG. 19, whereby the probe needle is deformed in an elastic manner. Tip 102 of the probe needle is shifted laterally on electrode 105. This causes aluminum oxide layer 118 at the surface of electrode 105 to be scraped off the surface of electrode 105. As a result, direct contact can be provided between aluminum layer 119 which is the main body of electrode 105 and tip 102 of the probe needle. Thus, tip 102 of the probe needle forms contact with electrode 105 in the conventional inspection process.
The scraped aluminum oxide layer 118 at the surface of electrode 105 leaves a probe vestige 106 where aluminum layer 119 is exposed, as shown in FIG. 30. FIGS. 30 and 31 show the probe vestige corresponding to the blast type probe needle of FIGS. 22 and 23. FIG. 32 shows the probe vestige corresponding to the specular probe needle of FIGS. 24 and 25. FIG. 33 shows the probe vestige corresponding to the spherical type probe needle of FIGS. 26 and 27. Referring to FIGS. 30 and 31, a protuberant portion 116 originated from the aluminum oxide scraped away is formed around probe vestige 106. Protuberant portion 116 has a height of approximately 10 .mu.m. Following the inspection process of this semiconductor device, electrode 105 is coupled to a bonding wire such as of gold by thermosonic bonding in order to be connected to a lead frame. As to this coupling, there is a problem that the bonding between electrode 105 and the bonding wire is degraded by protuberant portion 116 formed of aluminum oxide at the circumference of probe vestige 106 since the bonding between aluminum oxide and gold is weaker than the bonding between aluminum and gold. The bond between electrode 105 and the bonding wire is further aggravated if probe vestige 106 is greater in size. This is because the amount of aluminum oxide layer 118 scraped aside is proportional to the size of probe vestige 106, resulting in a greater protuberant portion 116 which is composed of the aluminum oxide. There was a problem that the reliability of the semiconductor device is degraded due to the insufficient bonding between the bonding wire and electrode 105.
Furthermore, if the scraped aluminum oxide adheres to tip 102 (refer to FIG. 29) of the probe needle, the contact between electrode 105 and tip 102 of the probe needle is obstructed. It will become difficult to properly transmit an electric signal between the probe needle and electrode 105. This will degrade the reliability of the inspection per se of the semiconductor device. As a result, the reliability of the quality of the fabricated semiconductor device will also be degraded.